This grant proposes to significantly advance the current technology for generation of mouse models of human genetic disease. This addresses broad Challenge Area (15) Translational Science, and Specific Challenge Topic 15-OD(ORDR)-101: Pilot projects for prevention, early detection and treatment of rare diseases. Although recent advances in human genetic technologies have revolutionized our ability to identify disease candidate genes, we currently lack sufficient high-throughput technology to economically and efficiently assess the relevance of candidate genes in in vivo follow-up studies in mice. We propose a new strategy to rapidly and inexpensively generate mouse models of human structural birth defects of the cerebellum and cerebrum (Dandy-Walker malformation, microcephaly) and severe congenital heart defects (Holt-Oram Syndrome and Conotruncal malformations). Each specific disorder we are modeling in this pilot study has a prevalence of between 1/100,000 and 1/5,000 births and is genetically heterogeneous, qualifying these as Rare Disorders. Since we are generating mouse models of rare brain and heart congenital malformations, this proposal is of direct interest to ODS, NINDS, NICHD and NHLBI. Notably however, this research will have a high impact in general biomedical science and public health and is likely of interest to multiple NIH institutes, since the new technology proposed will be applicable to the generation of mouse models for any human genetic disorder. This technology is especially relevant to NHGRI and other institutes who are supporting large scale human Genome-wide Association and CNV studies currently underway to indentify human disease candidate genes. This proposal combines recent parallel advances in RNAi technology, mouse chimera generation and focused mouse phenotyping into a novel strategy allowing inexpensive and rapid generation of efficient knock-down mouse models. We predict that initial knock-down phenotypes can be assessed in 2 months for approximately $2,000 per gene. This is approximately 1/6 the time and at least 10% of the current cost of standard mouse knock-outs. Rapid, efficient and inexpensive production of knock-down mice will not replace, but rather complement ongoing large scale NIH mouse ENU and genome-wide gene targeting programs. The time and financial economies however, that result from this novel knock-down strategy will revolutionize disease candidate gene analysis. Funding will permit rapid advancement in our understanding the pathogenesis of human disease which in turn, will improve disease diagnosis and treatment and additionally accelerate drug discovery. As a direct result of funding 1.5 new full time employment (FTE) positions will be created and 2 FTE positions will be retained. Although the Human Genome Project has allowed identification of many human disease genes, current technology to model human diseases in mice is time consuming and expensive and cannot keep pace with the current rate of human genetic discoveries. Described in this proposal is a new, inexpensive and rapid strategy to generate mouse models of human disease. This technological advance will enable more rapid understanding of the biological basis of human disease, improve disease diagnosis and facilitate treatment and drug discovery.